Magnetron construction



May 13-, 1958 P. P. DE RBY IVIAGNE'IRON CONSTRUCTION Filed Feb. 25, 1955 PALMER P; DERBY ATTO/ZNEV United States Patent MAGNETRON CONSTRUCTION Palmer P. Derby, Weston, Mass, assignor to Raytheon Manufacturing Company, Waltharn, Mass, a corporation of Delaware Application February 25, 1955, Serial No. 490,573

. 3 Claims. (Cl. 315-39) This invention relates to the construction of a magnetron to facilitate its coupling to a load, and more particularly to means for mounting a magnetron directly within a Wave guide or cavity resonator.

Early magnetrons had simple coupling'arrangements. However, these arrangements were inefficient due to radiation of the generated energy from such coupling means into free space. This was particularly true of such coupling means as simple leads from the cathode and anode. Such structures created problems of mismatch between the magnetron and the load. With the development of the multi-cavity magnetron, a carefully designed and precisely made and consequently expensive output structure was required.

In the present invention a magnetron enclosed in a vacuum tight envelope of dielectric material is inserted directly in a wave guide near one end or in a cavity resonator coupled by a wave guide or other transmission line to the load. The axis of the magnetron is positioned parallel to the electrical vector of the mode desired to be propagated in the wave guide. Leads from the filaments, the cathode and the anode are brought through the envelope and the wave guide wall to sources of operating potentials. Strapped anodes may also be used with this type of construction. Radiation is more efiicient if one strap is raised above the other to produce a radiating structure. An additional ring may be mounted on one or both sides of the anode structure to increase the radiation and coupling. Tuning structures and impedance matching devices of well-known types can be placed in the wave guide in the neighborhood of the magnetron or in the cavity in which the magnetron is placedf The wave guide itself prevents losses by radiation as does the cavity. Loading is adjustable by shifting the position of the magnetron within the wave guide or by making one of the walls of the cavity adjustable.

These and other advantages, features and objects of the invention will become more apparent from the following description taken in connection with the accompanying drawings wherein:

Fig. 1 is a vertical section through a wave guide and magnetron, built according to one embodiment of the invention;

Fig. 2 is a horizontal section through the embodiment of Fig. 1;

Fig. 2A is a section along the line 2A2A of Fig. 2;

Fig. 3 is a vertical section through the anode of the magnetron of Figs. 1 and 2 on an enlarged scale;

Fig. 3a is a section through a modification of the anode of Figs. 1 and 2.

In Figs. 1 and 2, the reference numeral designates the envelope of the magnetron 11 which has an anode structure 12 formed by an external shell 13 and radial vanes 14 which together form resonant cavities. A cathode 15 is located within the inner ends of the vanes 14 and concentrically mounted with its axis along the axis of the anode. trically within the cathode 15 and is connected by means A filament 16 is mounted concen- 2,834,914 P en e ila .915%

of electrodes 17 and 18' that pass through the envelope l0 and a base20 to the external circuit. There isv also a lead '21 on the cathode. and a lead 22 from the anode 12. to the. external circuit. The magnetron is mounted Within a rectangular'wave guide 23 with the axis of'the cathode and the an 'odedparallel to the narrow walls '24 and perpendicular tothe wide walls 25 of the wave guide23.'

It will be seen from Fig. 3 that the vanes 14 are formed with notches into which straps 19- and 19a fit. The strap 19 fits on one side of the vanes 14 and is connected to one set of alternate vanes and the strap 19a fits on the other side of the vanes 14 and is connected to the alternate set of vanes 14. This creates an unbalance and develops a voltage vector between the straps and propagates radio frequency energy down the guide with a voltage vector parallel to this vector. Fig. 3a shows a second Way of producing such an unbalance. A pair of straps is mounted in the usual manner on one side of the vanes but one extends further out than the other to create the desired unbalance and voltage vector for the propagated energy.

The electrodes 17, 18, 21, 22 and 26 support the magnetron proper 11 within the envelope 10. A ring 27 is connected to the anode 11 and supported by the electrode 26. This ring serves as a getter during the processing of the tube. The transverse magnetic field is provided by a U- or C-shaped permanent magnet 28. Inserts 30 and 31 of magnetic material may be positioned in the region where the poles 32 and 33 of the magnet 28 contact the wave guide 23 to reduce the reluctance of the magnetic circuit over what it would be if a non-magnetic material, such as copper or brass, of which the wave guide is usually constructed, were permitted to intervene at these points. The Wave guide 23 terminates in a flange 34 which is adapted to attach the wave guide to an additional length of wave guide. A circular piece 35 of tubing is attached to a plate 36 with a rectangular opening 37 which is in turn attached by soldering or otherwise to the wave guide 23 to receive the circular base 20. Other methods of bringing the electrodes out to the external circuit might be used. The anode and cathode could be supported by other means than their own leads. The impedance of the magnetron may be matched to that of the load by a matching screw 38 in a manner which is well known.

This invention is not limited to the particular details of construction, materials and processes described, as many equivalents will suggest themselves to those skilled in the art. It is accordingly desired that the appended claims be given a broad interpretation commensurate with the scope of the invention within the art.

What is claimed is:

1. In combination, an electron discharge device comprising a cathode, an anode structure spaced from said cathode, said anode structure at least partially defining a plurality of cavity resonators, means for applying a transverse magnetic field to the space between the said anode and cathode, a rectangular waveguide, means for producing an electrical unbalance across said anode parallel to its axis, and means for mounting said anode structure within said waveguide with its axis parallel to the electrical vector of energy propagated in the Waveguide.

2. In combination, an electron discharge device comprising a cathode, an anode structure spaced from said cathode, said anode structure formed with vanes at least partially defining a plurality of cavity resonators, means for applying a transverse magnetic field to the space between the said anode and cathode, means for producing electrical unbalance across said anode parallel to its axis comprising a pair of annular conductors contacting alternate sets of vanes and a rectangular waveguide, and means for mounting said anode structure within said waveguide with its axis parallel to the electrical vector of energy propagated in the waveguide.

3. In combination, an electron discharge device comprising a cathode, an anode structure spaced from said cathode, said anode structure formed with vanes at least partiallyv defining a plurality of cavity resonators, means for applying a transverse magnetic field to the space between the anode and the cathode, means for producing electrical unbalance across said anode parallel to its axis comprising a pair of annular conductors contacting alter- 4 nate sets of vanes, one extending further from the anode than the other, a cavity resonator, means for mounting said device Within said resonator, and means for transmitting radio frequency energy from said cavity to a load.

References Cited in the file of this patent UNITED STATES PATENTS Re. 23,480 Brown Apr. 29, 1952 2,489,131 Hegbar Nov; 22, 1949 2,680,827 Randall et a1. June 8, 1954 

